1. Field of the Invention
The present invention relates to an object (a product such as a machine, a manufacture, or a composition of matter) and a method (a process such as a simple method or a production method). For example, one embodiment of the present invention relates to a semiconductor device, a power storage device, a driving method thereof, or a manufacturing method thereof.
2. Description of the Related Art
In recent years, storage batteries such as lithium-ion secondary batteries have been widely used as power supplies for portable terminals typified by mobile phones and smartphones, power supplies for motor driven vehicles such as electric vehicles, and power supplies for uninterruptible power supplies.
For example, a power management device including a coulomb counter has been proposed as a device that manages the state of charge of a battery pack of a portable computer (Patent Document 1).